US12285200B2 - Length adjustable modular screw system - Google Patents

Abstract

A length adjustable modular screw includes a neck assembly and a shank. The neck assembly has proximal and distal ends and includes an expander component and a collet component that are slidably engagable by insertion of the expander component in a through channel of the collet component along a common axis. The length adjustable modular screw also includes a shank suitable for insertion and retention within a bone, the shank including a threaded portion between proximal and distal ends and a socket adapted to coaxially receive at least a portion of the distal end of the neck assembly. The length adjustable modular screw has a length that is selected by splaying at least a portion of the distal end of the engaged expander and collet components of the neck assembly within the socket of the shank.

Description

PRIORITY

The present application is a U.S. Patent Application which is a divisional of and claims priority to U.S. patent application Ser. No. 16/818,924 filed on Mar. 13, 2020 titled “LENGTH ADJUSTABLE MODULAR SCREW SYSTEM”, which is a continuation of and claims priority to U.S. patent application Ser. No. 16/018,942 filed Jun. 26, 2018 titled “LENGTH ADJUSTABLE MODULAR SCREW SYSTEM”, which is a continuation in part of and claims priority to Patent Cooperation Treaty Patent Application PCT/US2017/048480 filed Aug. 24, 2017 titled “ADJUSTABLE BONE FIXATION SYSTEMS”, which claims priority to and the benefit of U.S. Provisional Patent Application No. 62/379,111 filed Aug. 24, 2016 titled “ADJUSTABLE BONE FIXATION SYSTEMS”, each of which is hereby incorporated by reference in its entirety.

FIELD OF INVENTION

The present invention relates to modular and adjustable assemblies for achieving alignment and fixation of two or more bones or bone segments. In particular embodiments, the invention relates to modular and adjustable assemblies for achieving fixation of bones in the spine.

BACKGROUND

The human skeleton is formed of bones, each bone performing a structural role, either individually or collectively with other bones. For example, the spine, which surrounds and protects the spinal cord and associated nerves, provides structure to the body, and enables fluid movement in many planes. Constructed of essentially twenty-four stacked vertebrae, the spine includes seven cervical vertebrae, twelve thoracic vertebrae and five lumbar vertebrae. A healthy spine is flexible in multiple directions to enable a broad range of physical movement. Intervertebral disks are disposed between adjacent vertebrae and provide cushioning and dampening to protect the spinal column and nerves in response to the various translational and rotational forces associated with body motion. Maintenance of the structural integrity and approximate axial alignment of the vertebrae is one key to good health.

A clinical subject's spine may be damaged or otherwise compromised in one of many ways. Abnormalities of or damage to the spine include but are not limited to scoliosis (abnormal lateral curvature), kyphosis, excessive lordosis, spondylolisthesis, displaced, degenerative or ruptured discs, fractures to one or more vertebral bodies and tumors. These and other possible spinal conditions directly and adversely affect mobility, and also cause moderate to extreme or even debilitating pain, at times accompanied by diminished or lost nerve function.

To ameliorate pain and restore loss of function associated with spinal conditions, a variety of conventional procedures have been developed using an array of mechanical surgical systems and implants that can secure two or more vertebrae in a relatively fixed position and can stabilize and straighten spinal deviations along the spinal axis. A stabilization system can be used without fusion treatment of the spine, or in conjunction with fusion treatment of the spine wherein one or more spacing devices is used to replace all or a portion of a vertebral disc. Typically, such discal implants are used together with natural bone components obtained from the clinical subject or a donor source, artificial bone, other biologic components to promote bone growth and fusion between the adjacent vertebral bodies. One or more such replacements may be accomplished in a spinal fixation surgery. The fixation system, with or without fusion components, operates to create a substantially rigid construct of bone and mechanical hardware that replaces damaged or diseased vertebrae and connects them to relatively healthier adjacent vertebrae.

Generally, spinal fixation systems involve some mode of stabilization using one or more rigid or substantially rigid surgical stabilization elements, such as a rod or a plate, and means for fastening and securing the stabilization element to bone. Fastening means can include one or more bone anchors, such as screws or bolts, assembled with connectors that enable engagement with one or more stabilization elements. The connectors may include hooks, clamps, cross connectors and other structures that engage with one or more of stabilization elements and anchors. These systems of anchor and connector assemblies and stabilization elements are secured to two or more vertebrae and are interconnected to provide support, encourage alignment or realignment of the vertebrae, and to achieve immobilization and fusion.

When spinal fixation surgery is performed from the anterior aspect of the clinical subject, it is conventional practice to affix a stabilization element in the form of a thin plate, typically formed of metal, to adjacent vertebral bodies and secure the plate using anchors, such as screws. When the fixation surgery is performed from the posterior aspect of the clinical subject, it is conventional practice to affix bone anchors into the vertebral bodies, typically in the pedicle. Multiple levels of adjacent vertebrae may be fixed in this manner. Interconnection of the secured anchors to the stabilization element creates a rigid fixation between the adjacent vertebral bodies.

The mode of surgical access may be open, that is, involving a relatively extensive resection of the soft tissue to plainly expose the vertebrae to be fixated. In some examples, the mode of surgical access may be minimal, wherein less invasive surgical techniques are used to minimize tissue resection. These less invasive approaches have many benefits to the clinical subject, however, the associated reduction in direct access and visualization of the vertebral tissue practically means that the anchor implants are difficult to access, grasp and manipulate with instruments, thus complicating the surgeon's efforts and often prolonging the amount of time that the clinical subject is in surgery.

Among the many challenges associated with placement of vertebral stabilization systems is the fact that adjacent vertebrae are typically not perfectly aligned. Indeed, along any particular portion of a spine, a series of adjacent vertebrae can deviate laterally a great deal from the central axis of the spine. Further, as a result of natural spinal curvature and any vertebral defects, corresponding portions, such as pedicles, of adjacent vertebra are not in the same plane. In the context of implanting spinal fixation systems, these variations can be accommodated to some extent by introducing bends or curves in the substantially rigid stabilization element(s) used for fixation. But in instances where the therapeutic benefit is obtained by realigning adjacent vertebrae, adjustment of the curvature of the stabilization element(s) is not a completely satisfactory solution. Accordingly, it is typically the case that the surgeon and surgical team must manipulate the spine and the system instruments in an attempt to align the secured anchors for attachment to a stabilization element. Often, the extent of nonalignment, both in terms of longitudinal and vertical planar positions of vertebrae along the spine, can cause failure of one or more of the system components, extend surgery, cause damage to the clinical subject's spine, and ultimately lead to a less than desirable clinical outcome. The challenges of access in minimally invasive procedures can compound the difficulties associated with non-aligned vertebral bodies.

Attempts have been made in the design of spinal fixation systems to address variability of spinal anatomy, such as those variations described above. In many examples of conventional systems, anchors are adapted to achieve a range of variability in positioning based on pivotal rotation of the anchor such that the axis of the secured anchor relative to the stabilization element can be varied. These are referred to as poly-axial and uni-axial anchors. They are useful in particular for facilitating attachment of a stabilization element to two or more vertebrae that are not aligned along the spinal axis. There are other examples of systems that are adapted with features that facilitate engagement of non-axially aligned vertebrae. But there are no conventional systems suitable for accommodating the variability in the relative height of adjacent vertebrae, wherein corresponding portions of adjacent vertebrae are not on the same plane. Further, there are no conventional systems that allow the surgeon the option to install bone anchors into the bone and then select from a suite of modular anchor components to achieve an optimized system for fixation that avoids or minimizes the problems associated with anatomical variations in the spine. Beyond the spine, such as for other bones and bone fragments in the body, there are likewise no systems that provide either or both modularity and length adjustability options in the fixation or reduction of bones and bone fragments.

To address the above-described challenges, there is need for bone anchors and other implants that meet or exceed the functionality of conventional anchors while also providing adjustability, and ideally, modularity, to address the height variability of vertebral bodies that do not share a common plane. Thus, what is needed, for example in the context of the spine, is a fixation system that includes one or more anchors that are capable of mono-, uni-, and poly-axial positioning and allow substantial vertical travel between the distal attachment point in the bone and the proximal position of a stabilization element, and are capable of locking to avoid further vertical travel after the system implantation is completed. Such an anchor would enable simplified attachment of adjacent anchors to a stabilization element by reducing the extent of height variability of adjacent anchors, thereby avoiding many of the challenges faced in the surgical setting.

SUMMARY

The present invention describes various exemplary systems and methods of installation of one or more anchors and stabilization elements that are adapted for height adjustability during spinal fixation surgery. The disclosure is directed in various embodiments, both described and contemplated, to assemblies, subassemblies and modular components and their methods of use and installation for achieving adjustable fixation and/or reduction of bones and bone fragments.

Provided in various embodiments is a length adjustable modular anchor system and methods of use thereof for engagement with a bone. In an exemplary embodiment, the length adjustable modular anchor system includes a length adjustable modular screw that includes a neck assembly and a shank.

In various embodiments, the disclosure provides a length adjustable modular screw that includes a neck assembly that has proximal and distal ends and includes an expander component and a collet component that are slidably engagable by insertion of the expander component in a through channel of the collet component along a common axis. The length adjustable modular screw also includes a shank suitable for insertion and retention within a bone, the shank including a threaded portion between its proximal and distal ends and a socket adapted to coaxially receive at least a portion of the distal end of the neck assembly. The length adjustable modular screw has a length that is selected by splaying at least a portion of the distal end of the engaged expander and neck components of the neck assembly within the socket of the shank. The length adjustable modular screw is one of monoaxial, uniaxial, and poly-axial.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the disclosed inventions will now be discussed with reference to the appended drawings. These drawings merely depict representative embodiments and are not limiting in scope.

FIG.1 shows a front plan view (a.) and alternate perspective views (b. and c.) of a length adjustable modular anchor system according to the disclosure;

FIG.2 shows exploded (a.) and assembled (b.) perspective views of the neck assembly of the length adjustable modular anchor system shown inFIG.1;

FIG.3 shows a front plan view (a.), an exploded perspective view (b.) and a close up perspective (c.) view of the length adjustable modular anchor system shown inFIG.1;

FIG.4 shows on the left alternate top perspective (a.), side plan (b.), and partial close up side plan (c.) views of an expander component of the neck assembly shown inFIG.2, and on the right alternate top perspective (d.), bottom perspective (e.), and side cross sectional (f.) views of a collet component of the neck assembly shown inFIG.2;

FIG.5 shows an alternate side plan (b.), top, (a.) perspective (e.), and alternate side cross sectional (c. and d.) views of a shank component of the length adjustablemodular anchor system10 shown inFIG.1;

FIG.6 shows on the top a top plan view (a.), and on the bottom side plan (b.) and cross sectional (c.) views of the length adjustablemodular anchor system10 shown inFIG.1, and a top plan view (f.), side plan (d.) and cross sectional (e.) views of an alternate embodiment of a length adjustablemodular anchor system10 that includes a retaininghousing20, acompression washer30 and a lockingelement40 according to the disclosure; and

FIG.7 shows each, individually in alternate views, the retaining housing20 (a.), a compression washer30 (top perspective, b., and bottom perspective, c.), locking element40 (d.), and protuberance570 (e.).

TABLE
of Reference Numerals

	length adjustable modular	through slot 452
	anchor system 10	interference enhancer 454
	retaining housing 20	(e.g., groove/furrow/rib)
	compression washer 30 (e.g., cap)	leg 456
	locking element 40 (e.g., set screw)	compression element 460
	rod (not shown)	complementary taper 462
	length adjustable modular screw 100	shaped recess 470
	neck assembly 200	recess proximal stop 472
	mated 220	recess distal stop 474
	expander component 300	outer surface 480
	head 310 (hemispherical)	chamfered corners 482
	foot 320	collet cross sectional shape
	foot cross sectional shape 322	490 (e.g., square)
	pin 330	shank 500
	taper 332	threaded portion 510
	extension 334	proximal end 520
	circumferential flange 340	proximal aperture 522
	flange generally planar surface 345	proximal thread zone 524
	flange taper 347	distal end 530
	detent region 350	distal tip 532
	drive recess 360 (hex)	distal thread zone 534
	pin 330	socket 540
	cross sectional shape	socket cross sectional shape
	370 (e.g., sq/cyl)	542 (e.g., sq/cyl)
	collet component 400	chamfered sidewall 544
	proximal end 410	wall 550
	distal end 420	wall aperture 560, 560′
	through channel 430	protuberance 570, 570′
	inner wall 431	floor 580
	inner wall cross sectional shape 432	floor taper 582
	(cylindrical)	diameter 590 (e.g., straight,
	seat 440 (hemispherical)	tapered, step down)
	seat recess 441	major diameter 592
	seat recess cross sectional	minor diameter 594
	shape 442 (e.g.,	cannula 596
	sq/cyl)collet 450	flange 598

DETAILED DESCRIPTION

This Detailed Description describes exemplary embodiments in accordance with the general inventive concepts and is not intended to limit the scope of the invention in any way. Indeed, the invention as described in the specification is broader than and unlimited by the exemplary embodiments set forth herein, and the terms used herein have their full ordinary meaning.

The general inventive concepts will now be described with occasional reference to the exemplary embodiments of the invention. This general inventive concept may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concepts to those skilled in the art.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art encompassing the general inventive concepts. The terminology set forth in this detailed description is for describing particular embodiments only and is not intended to be limiting of the general inventive concepts. As used in this detailed description and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The term “proximal” as used in connection with any object refers to the portion of the object that is closest to the operator of the object (or some other stated reference point), and the term “distal” refers to the portion of the object that is farthest from the operator of the object (or some other stated reference point). A “clinical subject” refers to a human or other animal who is the subject of treatment with a bone fixation or reduction device in accordance with the disclosure. With respect to any references herein that may be made relative to a clinical subject, the term “cephalad” indicates a direction toward the head of the clinical subject, and the term “caudad” indicates a direction toward the feet of the clinical subject. The term “posterior” indicates a direction toward the back of the clinical subject, the term “anterior” indicates a direction toward the front of the clinical subject, and the term “lateral” indicates a direction toward a side of the clinical subject.

The term “height” as used specifically herein pertains to references to the spine of a clinical subject and refers to the relative position of one or both of vertebrae and anchors along adjacent portions of the spine. Likewise, the terms “vertical” and “vertical adjustment” relate to the relative height variations and adjustments thereof with respect to one or both of vertebrae and anchors along adjacent portions or the length of the spine in the context of a clinical subject in a prone position wherein a length adjustment to an anchor would be in a vertical dimension from anterior to posterior. These descriptors are not intended to be limiting with respect to embodiments of the modular adjustable assemblies, subassemblies and components according to the instant invention that are useful outside of the spine and may more generically be substituted with alternate descriptors including “length” and “length adjustment” where orientation of the clinical subject or body part and bones and implants vary.

As used herein in the described and illustrated embodiments, the term anchor typically refers to the screw component of an anchor assembly or subassembly, and the term anchor assembly refers to the screw component together with attachment features, such as a retaining housing (a conventional tulip head) or other type of attachment device, and one or more of compression washers and set screws, and optionally additional fixation components.

Subassemblies also refer to the modular components of the screw, such as, for example, the shank and head portions and subassemblies of these. More generically, anchor components, subassemblies and assemblies can be adapted to include features suitable for use with any bones in a clinical subject, wherein the modular and adjustable features are as described and claimed herein.

Unless otherwise indicated, all numbers expressing quantities of materials, properties such as length, diameter, and so forth as used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless otherwise indicated, the numerical properties set forth in the specification and claims are approximations that may vary depending on the suitable properties sought to be obtained in embodiments of the present invention. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the general inventive concepts are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from error found in their respective measurements.

Referring now to the drawings, an embodiment of a modular and length adjustablemodular anchor system10 for securing a bone stabilization element, such as a spinal stabilization rod, to a bone is depicted inFIG.1-FIG.6. As further described herein, the length adjustablemodular anchor system10 includes a length adjustablemodular screw100 which can be varied in length.

In accordance with the depicted embodiments, the length adjustablemodular screw100 is assembled to provide a construct that resembles a convention screw that includes ahead310 portion including at a proximal end410 a hemispherical screw head and a separate threadedshank500 portion including at a distal end a threadedshank500. In accordance with the disclosure, the length adjustablemodular screw100 components are adapted for interconnection along a common elongate axis and capable of vertical displacement to achieve fixed or variable length when implanted in a bone. In conventional pedicle screw anchors, pressure from the rod locked into the retaining housing20 (tulip head) by a threaded nut results in displacement of thecompression washer30 within thetulip head20 and compression on the head of the screw thereby transferring compressive force onto the screw, fixing it into place within thetulip head20 and preventing any axial rotation (for uni- and poly-axial assemblies).FIG.6 provides an example of such a system that includes an embodiment of a length adjustablemodular screw100 according to the disclosure. In use, the compressive force employed to lock a rod to a conventional screw also serves to lock the length adjustablemodular screw100 embodiments according to this disclosure, thereby fixing the vertical position selected by the surgeon.

Length Adjustable Modular Anchor System

Provided in alternate embodiments is a length adjustablemodular anchor system10 for engagement with a bone. In one embodiment, as shown inFIG.1, the length adjustablemodular anchor system10 includes a length adjustablemodular screw100 that includes aneck assembly200 and ashank500. Referring now toFIG.2, theneck assembly200 includes anexpander component300 and acollet component400. As assembled, a portion of theexpander component300 is insertable within a throughchannel430 in thecollet component400 along a common axis, as shown inFIG.2. Thecollet component400 throughchannel430 originates within theseat440 and extends through thedistal end420 of thecollet450. When engaged, thehead310 of theexpander component300 contacts the seat of thecollet component400 and thepin330 is passed through the throughchannel430. In some embodiments, as depicted in the drawings, theexpander component pin330 includes anextension334 that extends beyond thedistal end420 of thecollet450. In other embodiments, theexpander component pin330 may lack such anextension334 and thus, thepin330 may not extend beyond thedistal end420 of thecollet450.

Theexpander component300 and thecollet component400 are engagable in each of open, mated and compressed configurations. In the open configuration, theexpander component300 and thecollet component400 are engaged without thehead310 contacting theseat440 and thepin330 of theexpander component300 is coaxially engaged with and only partially inserted in the throughchannel430 of thecollet component400 and the expander andcollet components300,400 are freely movable along the common axis.

In the mated configuration, as shown inFIG.3 (center image), thehead310 is contacting theseat440 and thehead310 of theexpander component300 and theseat440 of thecollet component400 are mated but not compressed, and thepin330 of theexpander component300 is fully inserted in the throughchannel430 of thecollet component400. In each of the open and the mated configurations, thecollet450 is not splayed. In the compressed configuration, theexpander component300 and thecollet component400 are mated and thehead310 and theseat440 are contacted and in compression, and thecollet450 is splayed such that it has an overall greater diameter590 than in its non-splayed configuration. Each of the expander andcollet components300,400 include cooperating features that are compressible together to splay thecollet450.

Referring now toFIG.4, left, theexpander component300 includes ahead310 at a proximal end and apin330 that extends from thehead310 at a distal end. Referring again toFIG.4, right, thecollet component400 includes at a proximal end410 aseat440 that is matable with thehead310 of theexpander component300, and at a distal end420 acollet450 that extends from theseat440. In some embodiments, each of thehead310 of theexpander component300 and theseat440 of thecollet component400 are generally hemispherical in shape and mated220 to form a generallyspherical head310, the mated220pin330 andcollet450 features forming a generally rod-shaped extension from the sphere. Of course, it will be appreciated that in some embodiments, thehead310 andseat440 features may be other than hemispherical. As depicted, theexpander component300 has ahead310 that is generally hemispherical and includes a flat at its apex that includes adrive recess360 for engaging a driver. Any suitable shapeddrive recess360 may be employed for engagement with any of a variety of drivers.

As shown in the drawings, in some embodiments thehead310 of theexpander component300 includes afoot320 having a generally square cross sectional shape, and theseat440 of thecollet component400 includes acomplementary seat recess441 having a generally square cross sectional shape for receiving thefoot320 of theextender component300.

In the various embodiments, thecollet450 includes at least one throughslot452 oriented parallel to the common axis and along at least a portion of thecollet450 through thedistal end420. And in some embodiments thecollet450 includes a plurality of throughslots452 arranged circumferentially around thecollet450 and extending along at least a portion of the length of thecollet450 and through thedistal end420. As shown in the drawings, for exampleFIG.4, thecollet450 includes four throughslots452. In the depicted embodiment, thecollet450 has a generally square crosssectional shape490, and each of the throughslots452 are arranged, respectively, on a side of thecollet450 to form four legs. As depicted, thecollet450 has chamferedcorners482 and generally planar sides on its outer surface. And thecollet450 includes on its outer surface at itsdistal end420 an array ofinterference enhancers454. As shown, theinterference enhancers454 include a knurled texture. In other embodiments, the feature may include other textural elements, or may include one or more furrows, divots or ridges. Theinterference enhancers454 may enhance the contact with thewall550 of thesocket540 within theshank500 when thecollet450 is splayed. And theinterference enhancers454 may also enhance the flexibility of theshank500 for splaying. It will be appreciated that in some embodiments thecollet450 lackssuch interference enhancers454. And as shown in the depicted embodiment, thecollet450 includes at itsdistal end420 on eachleg456 and within the through channel430 acompression element460 that is generally block shaped with a proximally oriented taper or angle.

It will be appreciated that a variety of conventional features ofcollets450 are known in the art and may be selected to facilitate locking and compression and/or frictional engagement between acollet450 and engaged anchor components. In some instances, variations in the thickness ofwalls550 of one or more components can be employed to achieve compressive engagement. In other examples,collet450 features may include tapers along the length of engaging components. It will be understood that the features described herein are intended to be non-limiting and other features ofcollets450 known in the art may be used to achieve the inventive modular and adjustable anchors in accordance with the invention.

In some embodiments, at least one of theexpander component300 and thecollet component400 includes a locking feature that is engagable when thehead310 of theexpander component300 and theseat440 of thecollet component400 are mated220. In some such embodiments, as is shown, for example inFIG.2, the locking feature includes acircumferential flange340 on thepin330 of theexpander component300 that interferes with thedistal end420 of thecollet450 when the expander andcollet components300,400 are in the mated220 arrangement to limit displacement of theexpander component300. As shown in the drawings, thecircumferential flange340 is located at a position that is between the proximal anddistal ends410,420 and includes a generallyplanar surface345 on a proximal edge which abuts ataper347 that is angled toward the common axis from proximal to distal to form a generally conical taper shape. And as shown, thepin330 has a diameter at itsproximal end410 that is greater than the diameter at itsdistal end420.

In some embodiments, thepin330 of theexpander component300 also includes adetent region350, which is shown inFIG.2. As depicted, thedetent region350 has a diameter that is approximately the same as the diameter of thepin330 at thedistal end420. And as depicted, thedetent region350 is abutted at its proximal end by ataper332 that is angled toward the common axis from proximal to distal to form a generally conical shape and abuts at its distal end the generallyplanar surface345 of thecircumferential flange340. Referring again toFIG.4, thecollet component400 includes at least onecompression element460 within thecollet450 throughchannel430 for contacting thetaper332 of thepin330.

As shown in the drawings, for example inFIG.2, the at least onecompression element460 of thecollet450 is engagable within thedetent region350 of thepin330 of theexpander component300 when the expander andcollet components300,400 are mated220. In various embodiments, thecompression element460 extends into thecollet450 throughchannel430, and has a shape that is one of angled, radiused and squared. In various embodiments, thecompression element460 may be formed continuously and interrupted only by the throughslots452, and may be dome shaped, may have planercircumferential flange340 shape, may include one or more conical or beveled edges, and may be wedge shaped. And there may be more than onecompression element460 arranged along the length of the throughchannel430.

Referring again to the drawings, for exampleFIG.4, thepin330 has a crosssectional shape370 that is generally cylindrical and the throughchannel430 of thecollet component400 has aninner wall431 with an inner wall crosssectional shape432 that is cylindrical. It will be appreciated that in other embodiments, each of thepin330 crosssectional shape370 and the inner wall crosssectional shape432 may be other than cylindrical.

It will be appreciated that in other embodiments, theexpander component300 and thecollet component400 may include features that engage to mate and compress that are located at positions other than as shown in the drawings. For example, one or more of thecircumferential flange340 and thedetent region350 and thetaper332 on thepin330 may be positioned more proximally or more distally, and thepin330 may not include an extension beyond one or more of thecircumferential flange340 and thedetent region350 and thetaper332. Likewise, one or more ofcompression elements460 may be positioned more proximally or more distally within the throughchannel430 of thecollet component400.

As shown in the drawings, theexpander component300pin330 includes aconical taper332 between thedetent region350 and a proximal portion of thepin330, wherein the one ormore compression elements460 of thecollet450 comprises acomplementary taper462, whichcomplementary taper462, when pressed against thedetent region350proximal taper332 of thepin330, splays thecollet450.

Referring now toFIG.1,FIG.3, andFIG.5, the length adjustablemodular anchor system10 also includes ashank500 that includes a threadedportion510 between proximal anddistal ends520,530. As shown, theshank500 includes at its distal end530 adistal tip532 that may be bulleted (not shown) and is suitable for penetrating bone. Theshank500 includes at itsproximal end520 an aperture that is in communication with asocket540. Thesocket540 extends within theshank500 along a length from theproximal end520 toward thedistal end530 and is adapted for receiving at least a portion of thecollet450 of theneck assembly200. When the length adjustablemodular anchor system10 is assembled, theneck assembly200 is adjustably engagable within theshank500 to achieve variable length of the length adjustablemodular screw100.

In the various embodiments, the threadedportion510 of theshank500 may be continuous from the proximal to the distal ends520,530, or there may be a gap at either end that lacks threading, or a gap along the length that lacks threading. In the various embodiments, theshank500 includes at least a major and aminor diameter592,594, theminor diameter594 defined by the outer surface of theshank500wall550 excluding the threads, and themajor diameter592 defined by the threads. In some embodiments, one or both of the major andminor diameters592,594 may be straight or may be tapered. In some embodiments, there may be a step down from proximal toward distal such that there may be more than onemajor diameter592 and/or more than oneminor diameter594. In some embodiments, at least a portion of the length of theshank500 may taper from proximal to distal either continuously or may taper in a stepped down manner. In some embodiments, the threading may vary to provide aproximal thread zone524 that is different from adistal thread zone534.

Referring again to the drawings, the depicted collet has a crosssectional shape490 that is generally square and thesocket540 of theshank500 has a socket crosssectional shape542 that is square, each of thecollet450 and thesocket540 including chamferedcorners482 and chamferedsidewalls544, respectively. It will be appreciated that in other embodiments, each of the collet crosssectional shape490 and the socket crosssectional shape542 may be other than square and may be cylindrical.

As shown, for example inFIG.3, theshank500 includes at least one, and as depicted, includes twowall apertures560,560′ that are adapted for receiving aprotuberance570 through each for engagement with theneck assembly200, as described further below. It will be appreciated that in some embodiments,protuberance570 may be integrated with theshank500. And while the drawings show thepin330 insertable in anaperture560,560′ through aflange598 on theshank500, in some embodiments, theshank500 may lack aflange598.

In accordance with some embodiments, the length adjustablemodular screw100 further includes at least one locking feature on at least one of theneck assembly200 and theshank500 that engages to retain theneck assembly200 within theshank socket540. Referring now toFIG.3 andFIG.4, in some embodiments, the locking feature includes a shapedrecess470 along at least a portion of the length of thecollet component400 and acomplementary protuberance570 situated at theproximal end520 of theshank500. Theprotuberance570 extends into theshank socket540 and is engagable with the shapedrecess470 of thecollet component400. The locking feature prevents pull out of theneck assembly200 from theshank socket540. The locking feature also limits rotational motion of theneck assembly200 within thesocket540. As shown, the shapedrecess470 has a generally elliptical shape and is elongate from the proximal410 and towards thedistal end420 of thecollet component400. The shapedrecess470 includes proximal anddistal stops472,474. It will be appreciated that other shapes for the shapedrecess470 may be employed, and the shapedrecess470 may have a longer or shorter length along thecollet450.

Other features of theneck assembly200 engage with theshank500 to further stabilize the engagement. Referring again to the drawings, theexpander component pin330 includes anextension334 at its distal end, and theshank socket540 includes afloor580 andcannula596 extending from thefloor580 towards thedistal end530. Thedistal end420 of thecollet450 contacts thefloor580 to limit the distal passage of theneck assembly200 within thesocket540, and thecannula596 is adapted to receive theexpander component300 extension which aids in stabilizing against off axis motion of theneck assembly200 relative to theshank500. In some embodiments, the length of each of the extension of theexpander component300 and the shapedrecess470 of thecollet450 are selected such that when theneck assembly200 is displaced proximally to the limit of thedistal stop474, the extension is retained in thecannula596 to maximize off axis stabilization together with restriction on axis pull out. As is shown in the drawings, thefloor580 of theshank500 has a generallyconical floor taper582. In some embodiments, thefloor580 may have another shape, and may be planar, or have a spherical contour or another shape.

It will be appreciated that in alternate embodiments different or additional engagement features may be used that achieve the fixed engagement between subcomponents. Such engagement is useful to enable torsional engagement and actuation, such as with a driving tool, of one or more components while preventing other components from experiencing torsional force. Likewise, it is advantageous to employ engagement features that serve as stops to prevent disengagement of components by the application of shear force, such as pull out of axially aligned components.

Referring again toFIG.6, an embodiment of a length adjustablemodular anchor system10 for engagement with a bone is shown. The length adjustablemodular anchor system10 includes a length adjustablemodular screw100 comprising aneck assembly200 and ashank500, a rod (not shown) and at least one retaininghousing20 and a lockingelement40 for engaging and securing the length adjustablemodular screw100 and the surgical rod. Optionally, the length adjustablemodular anchor system10 also includes one ormore compression washers30 for engagement between the rod and a bone anchor. In use, one or more than one length adjustablemodular anchor system10 may be employed together with one or more conventional bone anchors, and additional components including surgical rods (or other stabilizing members, not shown), retaininghousings20, lockingelements40 and optional components such ascompression washers30. Arrays of anchors and rods may be used for example to stabilize adjacent vertebral bodies which may include placement of up to four or more anchors, two each within pedicles of adjacent vertebral bodies and engagement of a spinal rod to each of the pair of adjacent anchors to confer stabilization along the length of the spine.

Also provided according to the disclosure is a surgical method for installing a bone anchor system for spinal fixation. According to the method, the steps include in some embodiments selecting each of two or more bone anchors, at least one of which bone anchors is a length adjustablemodular anchor system10 that includes aneck assembly200 and ashank500, as described herein above, and at least one spinal rod defining a longitudinal axis, and two ormore retaining housings20 for engaging and securing a bone anchor and a surgical rod, and two ormore locking elements40 for securing a rod to a bone anchor, and optionally, one ormore compression washers30 for engagement between a rod and a bone anchor. Further according to the method, the steps include, either before or after seating theneck assembly200 in a retaininghousing20, assembling a length adjustablemodular screw100 system.

The steps for assembling a length adjustablemodular screw100 system include first engaging the expander andcollet components300,400 of theneck assembly200 into one of open and mated220 engagement, and inserting theneck assembly200 into theshank500socket540, then contacting thedistal tip532 of theshank500 with a bone. Thereafter, using a suitable driver, engaging thedrive recess360 of theneck assembly200 to compress the expander andcollet components300,400 and splay thecollet450. Thereafter, under continued compression, driving the threadedportion510 of theshank500 into a bone. Once theshank500 is inserted to the desired depth in bone, the steps include releasing the drive compression on thedrive recess360 of theneck assembly200 to thereby relieve thecollet450 from being splayed and thereby allowing translation of theneck assembly200 within theshank500.

Thereafter, either before or after provisionally securing a surgical rod into the retaininghousing20, the vertical height (length) of the length adjustablemodular anchor system10 may be adjusted by sliding theneck assembly200 along the common axis within thesocket540 of theshank500. Once the desired length and vertical height relative to adjacent anatomy and/or other anchors or implants is selected, the method includes tightening the fixation element within the retaininghousing20 to compress the rod against theneck assembly200 and to drive theexpander component300 and thecollet component400 into compressed engagement to splay thecollet450 within thesocket540 of theshank500.

In some embodiments of the surgical method, the length adjustablemodular anchor system10 is fully assembled prior to engagement of the threadedportion510 of theshank500 with bone. In yet other embodiments, the length adjustablemodular anchor system10 is provided pre-assembled. And in yet other embodiments, at least theneck assembly200 of the length adjustablemodular anchor system10 is provided pre-assembled with a retaininghousing20.

In some embodiments, the length adjustablemodular screw100 can be adjusted within a displacement range between zero mm to 20 mm, and more particularly 0 mm to 10 mm, including fractional increments therein, including 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 1.5, 2.0, and 2.5 up to and through 20.0 mm. Of course, other increments and ranges of travel are possible, and implementation thereof is well within the skill in the art.

It will be appreciated that in each of the various embodiments according to the invention, more than one length adjustable modular screw may be provided that are of varying lengths and therefore allow for an expanded range of length adaptability. Whether the length adjustable modular screw components are of fixed length or offered in ranges of lengths, such possible embodiments are particularly advantageous in that they provide options in some embodiments for providing preassembled bottom and top loading anchor assemblies, as well as anchor assemblies and subassemblies that may be assembled partially by the manufacturer or partially or completely by the surgeon, providing a range of options for achieving maximal flexibility in the surgical setting.

As described herein in accordance with the depicted embodiments, the components of the length adjustablemodular screw100 assembly that achieve locking of the length adjustablemodular screw100 to a rod can also actuate thecollet450 locking mechanism for fixing theneck assembly200 of the length adjustablemodular anchor system10 to theshank500 and optionally fixing the vertical position of the length adjustablemodular screw100 relative to the vertebra and the fixation system elements. Of course, in other embodiments, the means of achieving locking may be other than compression by the rod, and in yet other embodiments the locking means may be the same but the specific elements, such as the lockingelement40, rod andcompression washer30, may be varied.

Reference is made herein to fixation systems that include in the depicted embodiments anchors in the form of vertebral pedicle screws, and stabilization elements in the form of one or more surgical rods. It will be appreciated by those skilled in the art that the spine is but one example of a bone or bone system that may be the object of surgical correction, and thus, pedicle screws and rods are mere examples of the bone anchor, and vertebral stabilization system components contemplated herein. In other examples, anchors may be screws for engagement with a tether or other tensioning means, or with one or more plates or rods or combinations of these. And anchors and systems described herein may be suitable for other bones and bone systems in the body. Moreover, it will be appreciated that the mechanisms for adjustment of anchor length can be adapted for use with other anchor and fixation and stabilization elements used in orthopedic applications in the spine or in other parts of the body.

In one example, spinal rods may be made adjustable according to the features disclosed herein to enable tuned adjustment of rod length at the time of implantation or subsequently as spinal healing and or adjustment takes place, such as for adjustment of rod length in connection with scoliosis treatment. In yet other examples, adjustable anchors may be employed in the reduction or fixation of other bones, such as bones of the hand, or of the foot or in other locations where adjustment of the length of an anchor or other fixation element is desirable. One such example would be incorporation of adjustability features disclosed herein in dual threaded headless screws or screws, rods or pins with other head and threading configurations that are used for interconnecting and reducing fractured bone fragments or adjacent bones. Such anchors adapted according to the instant disclosure would enable tuned adjustment of implant length to accommodate anatomical variations in a clinical subject and achieve optimized anchor placement.

The invention is directed in various aspects to a system including assemblies and subassemblies, components including anchors and anchor components adapted for attachment to a bony structure of a clinical subject. In an exemplary embodiment wherein the use is in connection with fixation of the spine, wherein one, two or more such anchors in the form of screws are affixed to bones, for example, vertebral structures such as the pedicle, and each anchor is connected to a stabilizer such as a surgical rod that is inserted between the anchors. The anchors are novel in many respects owing to their modular nature and thus the options to provide the anchors in modular, sub-assembled and assembled forms provide a broad array of choices for the surgeon in devising the optimal surgical fixation plan.

In use by a surgeon, installation of the inventive components of the exemplary bone anchor system for spinal fixation described above includes: selecting two or more bone anchor assemblies or subassemblies, including assemblies and subassemblies selected from pre-assembled and top and bottom loading forms, wherein at least one anchor assembly includes an length adjustable modular screw; selecting a stabilization element; using a suitable driver to drive each of two or more anchors or anchor subassemblies into fixed engagement with corresponding vertebrae, wherein at least one anchor or anchor subassembly includes or is adapted to engage with modular components that allow length adjustability, including translation along the vertical axis of the anchor, so as to enable selection of the anchor length by the surgeon; engaging a proximal portion of the modular adjustable anchor, such modular portion selected from a pre-assembled or modular screw head and engagement seat, to provide a means to introduce the stabilization element into engagement with the anchor; optionally incrementally adjusting the length of the anchor so as to achieve engagement of the stabilization element in the anchor; sliding the stabilization element into place within the anchor; introducing a fixation element to at least temporarily fix the stabilization element within the anchor; optionally, adjusting at least the vertical position of the anchor to optimize its height orientation relative to the stabilization element and adjacent anchors; tightening the fixation element to compress the stabilization element within the anchor assembly, thereby fixedly engaging the modular components of the anchor so as to lock the position of the anchor and also lock its engagement with the stabilization element. This process is repeated for each adjustable anchor in the system, and conventional methods are used with conventional anchors.

It will be appreciated by one of skill in the art that the length adjustable modular screw described herein may be employed with components of a conventional spinal stabilization system, and may be used on a single vertebra, or traversing two or more vertebra, and may be used in conjunction with fusion or non-fusion treatment of the spine. Of course, in various examples, the anchors may be employed in isolation or in systems that include two or more anchors, connectors and stabilization elements, and the anchors may be deployed other than along the spinal axis. Thus, in other examples of use, two or more anchors may be used to secure one or more stabilization elements that extend either laterally or from an anterior to posterior aspect to traverse a vertebral body, or that wrap around one or more vertebral bodies, or combinations of these. And of course it will be appreciated that in some examples the assemblies and subassemblies, components, including anchors and anchor components, may be used in bones of the body other than the spine, and as such may be used individually, as a plurality, or in combination with other devices, and combinations of these.

Claims (14)

What is claimed:

1. A length adjustable modular screw comprising: a neck assembly that includes an expander component and a collet component, the neck assembly having proximal and distal ends, wherein the expander and collet components are slidably engagable by insertion of the expander component in a through channel of the collet component along a common axis, and a shank suitable for insertion and retention within a bone, the shank including a threaded portion between its proximal and distal ends and a socket adapted to coaxially receive at least a portion of the distal end of the neck assembly, wherein the length adjustable modular screw has a length that is selected by splaying at least a portion of the distal end of the engaged expander and collet components of the neck assembly within the socket of the shank.

2. The length adjustable modular screw according toclaim 1, wherein the expander component of the neck assembly includes an extension that extends beyond the distal end of the collet component of the neck assembly.

3. The length adjustable modular screw according toclaim 1, the expander component comprising an extension at its distal end, and the socket of the shank comprising a cannula extending towards the distal end, the cannula adapted to receive the expander component extension.

4. The length adjustable modular screw according toclaim 1, wherein the expander and collet components are matable at their proximal ends when the expander component is inserted in the through channel of the collet component.

5. The length adjustable modular screw according toclaim 3, wherein the neck assembly comprises a generally spherical head when the expander and collet components are mated.

6. The length adjustable modular screw according toclaim 1, wherein the expander component comprises a head at its proximal end and the collet component comprises a seat at its proximal end, wherein the head and seat, when mated form a generally spherical head on the neck assembly.

7. The length adjustable modular screw according toclaim 6, wherein each of the head and the seat are hemispherical.

8. The length adjustable modular screw according toclaim 1, wherein the length adjustable modular screw is one of monoaxial, uniaxial, and poly-axial.

9. The length adjustable modular screw according toclaim 1, wherein the neck assembly components are engageable from between an open arrangement and a compressed arrangement.

10. The length adjustable modular screw according toclaim 9, wherein the neck assembly in the open arrangement provides free movement of the expander component within the collet component along the common axis.

11. The length adjustable modular screw according toclaim 1, wherein the modular screw is engageable with a retaining housing that is configured for accepting a rod and a fixation screw.

12. The length adjustable modular screw according toclaim 1, wherein an elongate component of the expander assembly comprises at least one through slot extending, or a plurality of circumferentially arranged through slots, extending along at least a portion of the length of its distal end.

13. The length adjustable modular screw according toclaim 11, the one or plurality of through slots being disposed on the second elongate component.

14. A length adjustable modular screw comprising: a neck assembly that includes an expander component and a collet component, the neck assembly having proximal and distal ends, wherein the expander and collet components are slidably engagable by insertion of the expander component in a through channel of the collet component along a common axis, wherein the expander and collet components are matable at their proximal ends when the expander component is inserted in the through channel of the collet component, the expander component comprising a head at its proximal end and the collet component comprising a seat at its proximal end, wherein the head and seat, when mated form a generally spherical head on the neck assembly; and a shank suitable for insertion and retention within a bone, the shank including a threaded portion between proximal and distal ends and a socket adapted to coaxially receive at least a portion of the distal end of the neck assembly, wherein the length adjustable modular screw has a length that is selected by splaying at least a portion of the distal end of the engaged expander and collet components of the neck assembly within the socket of the shank.

Images